You may think about a project as a mirror of your Salesforce organization state that is copied to your computer for handy editing.
Each project is linked to a Salesforce organization, via the specified Salesforce account. Usually, this account is set up during project creation, but you may change it at any time.
In the terms of JetForcer,content is a set of files which you are retrieving from a Salesforce organization for working. These files organized in a hierarchy of sub-folders. The folder which is the highest in this hierarchy is called content root folder or content root (by default it is the project folder itself).
To manage or explore project files, use the Project View, which displays resources in a hierarchical tree view. Salesforce projects are organized into the following folders:
src – This folder contains all files retrieved during project creation. They are organized into folders, by type. For a list of types and folders, see Metadata Types.